Definately just keep it short & simple so you don't give yourself too much to do & get all stressed. Wouldn't bother with hiring equipment unless you've got a big enough house, the babies don't know they're at a party so it's more a simple get-together to mark the day.
Maximum 2 hours (in my experience any longer & the babies start getting fretful, not to mention us mums trying to cope with grumpy baby!) Not too many people/babies, provide nibbles/easy snacks & drinks for the adults and snacklets for the babies.
Personally I wouldn't bother with games unless you secretly WANT to do them yourself Definitely DON'T plan an outside party in October! If you keep it small & simple, if the weater is nice on the day you can just move it into the garden then.